It is proposed to throw further light on mechanisms of vitamin B12 absorption, transport, utilization, fate, and excretion. It is proposed to develop improved assay methodology for content in human body fluids and tissues of folate, folate binding proteins, vitamin B12, vitamin B12 binding proteins, as well as to throw further light on the sources, nature, and functions of binding proteins for nutrients, particularly vitamin B12 and folic acid. BIBLIOGRAPHIC REFERENCES: Herbert, V.: Vitamins: Too much of a good thing? In, Science Year, The World Book Science Annual, 1976. Field Enterprises Corp., Chicago, 1975, p. 315. Herbert, V.: Cyanocobalamin (vitamin B12) injection intervals in pernicious anemia. JAMA 231:765, 1975.